The document provides information on Paleolithic and Neolithic civilizations. During the Paleolithic, humans lived in small bands and subsisted through gathering and hunting. The climate fluctuated between warm and cool periods. In the Neolithic, humans began practicing agriculture around 6500 BCE, leading populations to increase and civilization to emerge. River valleys provided fertile soil for agriculture, and civilizations developed around irrigation systems, divisions of labor, calendars, forms of government, and writing. Culture and art advanced during this period as well.